[deniseportorreal]

Hi everyone i am new here so please call me out if i broke some type of rule

I'm studying for my chem I final and im' a bit confused on how to determine the boiling point of compounds.

I decided to practice on these three compounds:
HF, HI, HCl

I know from my chem professor that HF has the highest boiling point.

I understand that molecular weight & electronegativity plays a role in determining that.

So in my notes i have:

HF:    molecular weight: 20, electronegativity: 1.9
HI:     molecular weight: 127, electronegativity: 0.4
HCl:   molecular weight: 36.46, electronegativity: 0.9

Can i determine the boiling point from these numbers alone or am i missing something???

Thank you
D

[deniseportorreal]

Anyone? 

[DrCMS]

HF's higher than expected boiling point is one of the classic examples of hydrogen bonding.

[kevinkevin]

  Well in order to determine the boiling point of the solutions you will need to know the molality of each one.  Then use the boiling point elevation equation.  If you do not need to find the exact boiling point then you look at the intermolecular forces between them.  The stronger the intermolecular forces between the molecules the more energy it will require to make them go into the gaseous phase, therefore they will have a higher boiling point. So the chart of electronegativities that you have could be use full.       

[Borek]

Well in order to determine the boiling point of the solutions you will need to know the molality of each one.

Hes is not asking BP of the solution, but of a pure compound.

And what he calls electronegativity is not electronegativity per se, but diiference in electronegativity between atoms. This will to some extent reflect possible dipole moment of the AB type molecules, and higher dipole moments will usually mean stronger intermolecular forces - so a higher BP. But it is just a handwavy argument, which doesn't have to give correct predictions in general.